The invention relates to pipe joints and couplings, but more particularly, the invention relates to a coupling member with a swivel nut and a resistive stop in conjunction with a frustoconical surface or flexible lip sealing means.
U.S. Pat. No. 5,002,316 to Chohan discloses a coupling member with a flexible lip that is effective as a sealing means when used in conjunction with a convex, tapered surface of a second coupling member that is commonly referred to as a flare type fitting. Most flare type fittings have a tapered or frustoconical surface at an angle of 37 degrees or 45 degrees. While coupling members of the type disclosed in the '704 patent have proved useful in effecting a fluid type seal when used with a flare fitting, they are subject to being over-tightened particularly for coupling sizes of less than 3/4 in. Over tightening may occur because such couplings offer very little tactile feel to an operator when torquing a swivel nut to effect a seal with a flare type fitting. Coupling members below 3/4 in. are susceptible to over torquing because the flexible lip operates at a smaller diameter and thereby provides less resistive torque than larger diameter fittings. Also, a swivel nut for the smaller swivel nut may have more threads per lineal inch than a larger nut and thereby has a greater mechanical advantage.
U.S. Pat. No. 3,672,704 to Christensen discloses a flexible lip fitting where the flexible lip is pressed against a non-standard, concave type frustoconical sealing surface. While the '704 fitting includes a positive stop which would preclude over-torquing of the coupling members during interconnection, the design requires the coupling members to be used in conjunction with each other as specially designed parts; in other words, the member with the lip seal could not be used in conjunction with a standard flare type fitting having a convex frustoconical sealing surface.